The purpose of this study is to demonstrate that the metabolic ratios of dextromethorphan and debrisoquin correlate. Then a safe and readily available method would be available to accurately measure 2D6 isoenzyme activity. This methodology could then allow researchers and clinicians the ability to quantify isoenzyme activity for use in predicting a starting or maintenance dose schedule of 2D6 metabolized. Toxic or subtherapeutic empiric doses could potentially be avoided.